The invention relates to a system for reducing non-linear distortions for an amplifier stage output signal of an amplifier stage.
To compensate for non-liner distortions amplifier stages are embodied in accordance with what is known as the “feed-forward-principle”. Here in a main branch of the amplifier stage an amplifier stage input signal is routed via a non-ideal amplifier of which the non-linearly distorted output signal is routed with a delay to an adder and on the other side is routed to an auxiliary branch.
The amplifier stage input signal is also routed to the auxiliary branch where an error signal is obtained from the non-runtime-delayed amplifier stage input signal and from the non-linearly distorted output signal of the amplifier which is routed to the adder for distortion compensation. From the error signal and the non-linearly distorted output signal of the amplifier the added forms the amplifier stage output signal, in which case the error signal compensates for the non-linear distortions of the amplifier.
With the “feed-forward principle” the non-linearly distorted output signal of the amplifier must be correspondingly delayed in accordance with a group delay time needed to determine the error signal in the auxiliary branch. A delay of this type is generally realized using a delay line with finite electrical quality. The delay line exhibits electrical losses which in their turn make the efficiency of the amplifier stage worse.
To reduce the losses a correspondingly complex and expensive implementation of the delay line is necessary in which further attenuations are caused by the delay line.